System for rapidly changing clamping jaws on a machine tool

ABSTRACT

A system is provided for the rapid change, among others, of clamping jaws on a machine-tool which comprises self-blocking means for locking a jaw for clamping a workpiece from the inside or a jaw for clamping a workpiece from the outside. The jaw-holder is provided with at least two bearing portions for said jaws, the bearing faces being slanted through an angle α and γ respectively. These faces cooperate in the blocked position with corresponding bearing faces of the jaws. One of the ends of an assembly has a face slanted through an angle β whereas another face is slanted through an angle δ. These faces cooperate in the blocked position with a corresponding bearing face respectively of one of the jaws.

BACKGROUND OF THE INVENTION

The present invention relates to a system for rapidly changing the clamping jaws on a machine-tool, which may be used for clamping the workpiece to the clamped not only from the inside but also from the outside, for use in repetitive and successive machining operations from the outside or inside the workpieces.

In French Patent Application 85/10958 of Jul. 17, 1985 (corresponding to U.S. Pat. No. 4,763,906), the Applicant described a system for rapidly changing the clamping jaws on a machine tool, comprising self-locking means for locking the jaws M on the jaw-holder P. The self-locking means is formed essentially by a locking element 1 having a base 1₁ on abutment face 1₁₀ of which said jaw M rests in the locked position and a bearing portion 1₂ for the jaw M, a bearing face 1₂₀ of bearing portion 1₂ is slanted through an angle α with respect to a horizontal plane perpendicular to the plane vertical to said face 1₁₀ of said base 1₁ for cooperating in the locked position with a corresponding bearing face M₂₀ of the jaw M on the one hand and, on the other hand, by at least one assembly 2 for maintaining said jaw in the locked position. One of the ends 2₁₀ of a mobile member 2₁ of said assembly 2 has at least one pushing face 2₁₀₀ slanted through an angle β with respect to a horizontal plane perpendicular to the plane vertical to said face 1₁₀ of said base 1₁ for cooperating, in the locked position, with a corresponding bearing face M₂₀ of the jaw M, said angles α and β being open in the same direction, said angle α being greater than said angle β. The assembly 2 further comprises means 2₁, 2₂ for unblocking ande unlocking said jaw M (see FIG. 1).

The angle α is 1.4 to 2 times the angle β and the difference between the angles α-β is of the order of 7° to 10°.

    α=1.4÷2;α-β:7°÷10°

The size of angle α is preferably from 15° to 30° and that of angle β is preferably from 7° to 20°.

The device described in that patent does not allow the jaw to be used from clamping from the outside and/or from the inside of the workpiece to be machined thus requiring the jaw-holder to be changed and/or the jaws for each machining mode. The result is a considerable loss of time, complication due to the multiplicity of jaw-holders and jaws required, and a relatively high production cost.

The object of the present invention is to overcome these drawbacks.

SUMMARY OF THE INVENTION

In accordance with the present invention, the system for rapidly changing, interalia, clamping jaws on a machine-tool is characterized in that it comprises self-blocking means for locking a jaw M₁ for clamping a workpiece from the inside or a jaw M₂ for clamping a workpiece from the outside on a jaw-holder P, these means being formed essentially by a blocking element having an abutment face against which the jaws M₁, M₂ rest in the blocked position and at least two bearing faces for said jaws M₁, M₂, the bearing faces being slanted through an angle α and γ respectively with respect to horizontal planes H₁, H₂ perpendicular to the plane vertical to the face of the base for cooperating in the blocked position, with corresponding bearing faces of the jaws M₁, M₂ on the one hand and, on the other, by at least one retainer for holding said jaws M₁ or M₂ in the blocked position. One end of the retainer has a bearing face slanted through an angle β with respect to a horizontal plane H₃ perpendicular to the plane vertical to the abutment face whereas another bearing face of the pusher is slanted through an angle δ with respect to a horizontal plane H₄ for cooperating in the blocked position with the corresponding bearing face respectively of one of the jaws M₂ or M₁. The angles α, β, γ, δ, are open in the same direction, the angles α, γ are larger than the angles β, δ, respectively. The assembly further comprises means, known per se, for unblocking and unlocking one of the said jaws M₁, M₂.

Planes H₁ and H₂ are at a distance R₁ and R₂ respectively with respect to a horizontal plane passing through the axis A--A of the mandrel, R₁ being larger than R₂, the plane H₁ being situated at a distance a from a horizontal plane passing through the axis x--x of the assembly 2 for holding a jaw M₁, M₂ in the blocked position, whereas the plane H₂ is a distance b from the plane passing through the axis x--x.

Plane H₃ is at a distance r₁ from the horizontal plane passing through the axis A--A and the plane H₄ is at a distance r₂ from plane passing through the axis A--A, r₁ being larger than r₂ ; said planes H₃ and H₄ being at a distance c and d respectively with respect to said plane passing through a axis x--x.

The distance a may be equal to b.

The distance c may be equal to d.

Angle α may be equal to the angle γ.

The angle β may be equal to the angle δ.

Finally, each jaw M₁, M₂ comprises a heel which, during blocking and locking of one of jaws M₁, M₂, is housed in a corresponding recess in the peripheral part of the base of the element of the jaw-holder.

Other advantages and features will be clear from the following test and the accompanying figures, given solely by way of example.

The text and the figures relate to a mandrel such as used in machine-tools where, in general, the workpiece to be machined and/or the tool are driven with a rotary movement. This system for the rapid change of a removable member on a fixed member, such as a jaw on a jaw-holder, may however be used within the scope of the invention for clamping very different workpieces, for example on a planer, a shaper, assembly installations, or the like after making the modifications necessary for adapting the system of the invention to the desired use.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows in section a system such as described in French patent 85 10958,

FIG. 2a shows in section a system in accordance with the invention for clamping a workpiece from the inside,

FIG. 2b shows in section a system in accordance with the invention for clamping a workpiece from the outside,

FIG. 2 shows a cross section passing through the axis x--x of the assembly of the system of the invention,

FIG. 3 shows in perspective a jaw-holder of the system of the invention, and

FIGS. 4a, 4b, 4c show in perspective jaws for clamping workpieces from the inside, from the outside and a jaw blank.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The principle of blocking and locking the jaws (self-locking) on the jaw-holder is substantially identical to that described in the above referenced French patent application 85 10958, permitting a very great repetitivity of the operation, with high accuracy of fitting the jaw on the jaw-holder and very low wear of the members forming part of the rapid exchange system.

As is shown in FIGS. 2a, 2b, 2c and 3, the jaw-holder P is formed so as to be able to be used for inside clamping jaws M₁ for clamping a workpiece (not shown in the drawings) from the inside or for inside clamping jaws M₂ for clamping a workpiece from the outside.

In fact, the jaw-holder P comprises a blocking element 1, an assembly 2 for holding the jaws M₁ or M₂ in the blocked and locked position, a toothed zone 3, for example on the lower face of the element 1 for holding the jaw-holder P in position on the mandrel (not shown in the drawings) whose main axis is A--A. The jaw-holder P is fixed on the mandrel by screws 4₁, 4₂ or similar fasteners.

The element 1 comprises a base 1₁ and bearing portions 1₂₁ and 1₂₂ for the jaw M₁ and the jaw M₂ respectively. These bearing portions are defined on the jaw M₁ side by a bearing face 1₂₂₁ slanted through an angle γ with respect to a horizontal plane H₂ perpendicular to the plane vertical to the face 1₁₀ of said base 1₁ ; and on the jaw M₂ side by a bearing face 1₂₁₁ slanted through an angle αwith respect to a plane H₁ which is a perpendicular to a vertical plane defined by the abutment face 1₁₀.

The assembly 2 comprises essentially a cylindrical jacket in which a retainer or pusher 2₁ may move under the action of a spring 2₂, along the axis x--x, which pusher has a substantially conical front end or head 2₁₀ or two planes slanted through an angle β and δ respectively. A groove 2₅ may be provided in pusher 2₁ for holding it in the blocked and locked position or in the unblocked and unlocked position by means of a finger 2₆ screwed into the fixed element 1. As has already been mentioned above, an (upper) portion of the head 2₁₀ has a bearing face 2₁₀₀ slanted through an angle β with respect to a horizontal plane H₃ perpendicular to the plane vertical to face 1₁₀, and a (lower) portion of head 2₁₀ has a bearing face 2₁₀₁ slanted through an angle δ with respect to a horizontal plane H₄.

Each jaw M₁ and M₂ comprises at one of its ends slanted or inclined reaction faces M₂₃, M₂₄ adapted to be contacted by the bearing faces 2₁₀₀ and 2₁₀₁ of the pusher 2. Each jaw M₁ and M₂ also includes at one of its ends a slanted contact face M₂₁ and M₂₂ respectively; the slant angle of face M₂₂ is equal to the slant angle γ of face 1₂₂₁ of element 1 and the slant angle of face M₂₂₁ is equal to the slant angle α of face 1₂₁₁ of element 1. In the blocked position of jaw M₁ on the jaw-holder P, i.e., when the contact face 2₂₀₁ pushes against the reaction face M₂₄, the slanted face M₂₂ of jaw M₁ cooperates with the slanted face 1₂₂₁ of the jaw-holder P; similarly, in the blocked position of jaw M₂ on the jaw-holder P, wherein the contact face 2₁₀₀ pushes against the reaction face M₂₃, the slanted face M₂₁ of jaw M₂ cooperates with the slanted face 1₂₁₁ of the jaw-holder P. The other end of each jaw M₁ and M₂ comprises a heel M₄₀₁ and M₄₀₂ respectively which is housed, in the blocked position, in one of the recesses 1₁₁ and 1₁₂ respectively; these recesses are formed diametrically opposite in the periphery of the base 1₁ of element 1. It is thus possible to fit on jaw-holder P either at least one jaw M₁ for clamping from the inside, or at least one jaw M₂ for clamping from the outside a workpiece to be machined, for example. To provide blocking and locking of jaw M₁, in the locked position, a slanted face M₂₂ of jaw M₁ cooperates with the slanted face 1₂₂₁ of jaw-holder P, the slant angle γ of faces M₂₂ and 1₂₂₁ being identical. Similarly, in the locked position of jaw M₂, its slanted face M₂₁ cooperates with the slanted face 1₂₁₁ of jaw-holder P, the slant angle α of faces M₂₂ and 1₂₂₁ being identical.

The horizontal planes H₁, H₂, H₃, H₄ are at distances R₁, R₂, r₁ and r₂ from a horizontal plane passing through the longitudinal axis A--A of the mandrel: R₁ >r₁ >r₂ >R₂. The planes H₁ and H₂ are at distances a and b respectively from a horizontal plane passing through the axis x--x, and the planes H₃ and H₄ at distances c and d respectively from this same horizontal plane passing through the axis x--x. The distance a-c is therefore equal to R₁ -r₁. The angle α is always greater than the angle β and the angle γ is always greater than the angle δ.

It is thus possible, by modifying, depending on the needs, at least one of the distances R₁, r₁, r₂ an dR₂ t form a range of jaws for clamping a workpiece from the inside or from the outside. In particular, for a=b and c=d, the angle α is equal to angle γ and the angle β is equal to the angle δ; this permits the use of the same jaw for clamping a workpiece from the inside and/or from the outside.

Numerous modifications and/or improvements may be made to the systems described above without departing from the scope of the invention. 

What is claimed is:
 1. A workpiece holding mechanism adapted for a rapid interchange of inside and outside clamping jaws which clamp workpieces from the inside and outside, respectively, of the workpieces; said mechanism including a locking element having an abutment face against which a respective jaw rests when in a blocked and locked position, said blocking element including first and second bearing faces inclined at first and second angles, respectively, relative to imaginary planes disposed perpendicularly to said abutment face; said inside and outside clamping jaws each having an inclined contact face arranged to engage the respective one of said first and second bearing faces when a respective jaw is in a blocked and locked position; retaining means for retaining a respective jaw in a blocked and locked position comprising a retaining member having at one end thereof third and fourth bearing faces inclined at third and fourth angles, respectively, relative to imaginary planes disposed perpendicular to said abutment face, each of said inside and outside clamping jaws including an inclined reaction face arranged to be engaged by a respective one of said third and fourth bearing faces such that when said reaction face of said inside clamping jaw is engaged by said third bearing face said contact surface of said inside clamping jaw is urged against said first bearing surface, and when said reaction face of said outside clamping jaw is engaged by said fourth bearing face said contact surface of said outside clamping jaw is urged against said second bearing surface; all of said first, second third, and fourth angles being open in the same direction; said first and second angles being larger than said third and fourth angles, respectively; and means for enabling said retaining means to be released relative to said reaction surface of a respective jaw for unblocking and unlocking said jaw.
 2. A mechanism according to claim 1, wherein said blocking element is situated against a longitudinal first axis defined by a mandrel, said second blocking face disposed farther from said first axis than said first blocking face, said retaining means comprising a pusher member movable along a second axis, said first and second bearing faces spaced from said second axis on opposite sides thereof.
 3. A mechanism according to claim 2, wherein said fourth bearing face is disposed farther from said first axis than said third bearing face, said third and fourth bearing faces spaced from said second axis on opposite sides thereof.
 4. A mechanism according to claim 2, wherein said first and second bearing faces are spaced equal distances from said second axis.
 5. A mechanism according to claim 3, wherein said third and fourth bearing faces are spaced equal distances from said second axis.
 6. A mechanism according to calim 1, wherein said first and second angles are equal.
 7. A mechanism according to claim 2, wherein said third and fourth angles are equal.
 8. A mechanism according to claim 1, wherein said blocking element includes first and second recesses, said first recess disposed closer to said first axis than said second axis, said inside clamping jaw including a first heel arranged to be received in said first recess, said outside clamping jaw including a second heel arranged to be received in said second recess. 